1. Field of the Invention
This invention relates generally to penetrometers and more specifically to such penetrometers utilizing the doppler effect.
2. Description of the Prior Art
Penetrometers have been used for years to gather technical information concerning sea floor characteristics. Prior art instrumentation utilized accelerometers, signal conditioning equipment, amplifiers and recorders which were packaged in single atmosphere enclosures attached to the accelerometer. The cost of the instrumentation was high and it was necessary to recover the penetrometer and instrumentation package. This was done by attaching a load bearing cable to the vehicle to recover it after completion of its mission. This cable, capable of pulling the vehicle from the ocean bottom, produced drag as the vehicle fell toward the bottom which reduced its terminal velocity, thereby restricting its usefulness. Tape recorders, due to the high gravity forces encountered during deceleration are not capable of properly recording the data.
Another prior art method used the same costly instrumentation attached to an expendable penetrometer. Electrical analogs of the desired parameters are transmitted over a very small cable consisting of several wires. The breaking strength of this cable is 1/2 pound. It is spooled on two spools; one riding the vehicle and the other on the surface ship, both paying out cable simultaneously. Its success depended on the integrity (physical and electrical) of the spool cable. Electrically, the cable is basically a low pass distributed, constant, resistance-capacitance filter undesirable for the purpose of transmitting information from the penetrometer to the surface. Failure occurred due to breakage of the conductors in the environment.